Hen egg is a staple food formulation ingredient in many food areas, including pet foods. It provides functional and nutritional fat, primarily via the yolk, and functional and nutritional protein, primarily via the albumen (or ‘white’).
The egg albumen is valued for its ability to form stable gels, to bind water and as a whipping agent to provide stable foams in food systems. The egg yolk is primarily valued as an emulsifying agent.
It is also known that if the egg white contaminates the egg yolk, it will tend to have a deleterious effect on this emulsifying ability. Equally, if the albumen is contaminated by the fat (from the yolk), this will dramatically reduce the functionality of the albumen, making it ineffective as a gelling or whipping agent.
In order to simplify the disclosure of the invention, reference will be made in this document to a ‘typical’ whole egg product, which will be familiar to those skilled in the art. The typical whole egg product comprises approximately 30% ‘wet’ yolk and 70% ‘wet’ albumen by mass. The yolk itself is comprised of approximately 50.8% solids and 49.2% water by mass; the albumen is comprised of approximately 11.8% solids and 88.2% water by mass (or put another way a water:solids ratio of about 7.5:1.
The total combined whole egg solids comprise approximately 24.2% by mass and the total water in the whole egg is approximately 75.8% by mass. While these numbers may differ in individual eggs, they are well known reference points for the content of hen eggs.
An important consideration in the supply of these egg components is the ability to provide a sufficient shelf-life for the storage and transport of the products before use. In the liquid form, the shelf life of the egg components is quite short. Pasteurising the liquid egg is known in the art. Typically, the liquid egg may be pumped through a heat exchanger at, for example, 64° C. for approximately 3 minutes, in order to produce, for example, a nine log cycle reduction in the occurrence of Listeria monocytogenes in the dried albumen or in the liquid egg. However, this temperature is not optimal for maintaining functionality, particularly of the albumen, as a substantial proportion of the albumen proteins will tend to denature at this temperature. However, this temperature is maintained in order to ensure sufficient heat treatment of the yolk and the albumen.
This method also does not offer the opportunity to optimise the usage of the white and yolk relative to one another.
Another well-known approach to the issue of providing enhanced shelf-life to egg products, whether whole egg or individual components such as yolk and albumen, is to dry the product. Typically, the albumen might be spray dried. In addition, the albumen might be pasteurised in either the wet or dry state to further promote the shelf life. This dramatically increases shelf life, but with a concomitant increase in the cost of the materials, due to the processing cost, and a potential lowering of functionality, due to heat denaturation of the proteins.
The dried whole egg, or combination of dried egg yolk and albumen, is then incorporated into the food product formulation. It replaces whole egg at a level which would replicate the level of yolk solids and albumen solids which would be provided by the whole egg being replaced.
In all applications of which the inventors are aware, this leads to the practice of incorporation of dried albumen and dried yolk at an equivalent ‘wet’ solids ratio of about 70:30, as per the typical wet whole egg composition, and an addition of ‘replacement’ water in the formulation at a ratio of about 3:1 to total egg solids added. Put another way, on a dry solids basis the typical formulation represents an egg albumen solids to egg yolk solids ratio of approximately 1:0.54.
However, this often means an overall increase in formulation cost, as the recombination of egg yolk, egg albumen and water inevitably carries a higher material cost than that of whole egg that is processed unseparated.
Accordingly it is an object of the invention to provide alternative formulations for food products containing dried egg yolk and dried egg albumen with optimised raw material formulation cost.